Carboxy-hydroxy-containing copolymers



United States Patent ABSTRACT on THE DISCLOSURE A copolymer of anunsaturated aliphatic acid having only one carboxy group, atleast onedifferent ethylenically unsaturated monomer and a beta-hydroxyalkylester of an unsaturated aliphatic acid having. only one carboxyl group,said copolymer being useful in coating compositions.

This invention is a continuation-in-part of my copending applicationSer. No. 364,274, filed May 1, 1964 now abandoned and application Ser.No. 117,830, filed June 19, 1961, now abandoned and application Ser. No.593,- 340, filed June 25, 1956, now U.S. Patent No. 3,002,959.

This invention relates to carboxy-hydroxy copolymers which are eminentlysuitable as crosslinking agents with diisocyanates, epoxides andaminoplast resins. More particularly, this invention relates to suchcopolymers having an acid value of from about 1 to 50.

The carboxy-hydroxy copolymers of this invention are estersof acopolymer of a shortchain alpha-beta unsaturated mono-carboxylic acidand a vinyl monomer having a single active terminal vinyl group, whereinthe ester substituents are formed by means of a monoepoxide. Thereactions involved in the preparation of these c'arboxyhydroxycopolymers are the carboxy-epoxy reactions between the carboxyl group ofthe alpha-beta unsaturated acid and the mono'epoxide, whereby thehydroxy ester is formed, and the copolymerization reaction whereinthe unsaturated mono-carboxylic acid, or its ester, and the vinyl monomercopolymerize to form the copolymer.

' In the reaction of a carboxyl group with an epoxide group, twomonohydroxy ester substituents are possible. Each portion of the ester'substituent derived from the monoepoxide, that is, the alcoholicportion of the ester snbstituent, contains one alcoholic hydroxyl groupon a carbon atom either alpha or beta to acarbonyl carbon atom. Hence,in the copolymers resulting from the process of this invention, eachhydroxyl in the molecule is attached to a carbon atom linked to acarbonyl group through the oxygen atom or to a carbon atom adjacent to acarbon atom linked'to a carbonyl group through the oxygen atom of theester linkage.

In preparing the copolymers of this invention, one method is to esterifythe alpha-beta unsaturated monocarboxylic acid to form the hydroxy-esterand then to copolymerize this resulting hydroxy-ester' with the vinylmonomer. Another method is to copolymerize the alphabeta unsaturatedmonocarboxylic acid with the vinyl monomer and then to esterify thecopolymer thus formed using a monoepoxide to form the carbox'y-hydroxyco polymer. A sufficient amount of the acid is used so that the acidvalue of the resulting copolymer is at least about 1. The upper limitfor the acid number is not critical and may be as high as 40 or even 50.Advantageously, the acid value is between about 12 and 20.

In accordance with Ser. No. 593,340, now U.S. Patent 3,375,227 PatentedMar. 26, 1968 No. 3,002,959 however, it was discovered that thehydroxy-ester and the copolymer can be made by concomitant reactions,through the combination of the three re actants and the use of twocatalysts, a carboxy-epoxy catalyst and a vinyl polymerization catalyst.Thus, by the use of two catalysts, a carboxy-hydroxy-containingcopolymer is prepared by copolymerizing an alpha-beta unsaturatedmonocarboxylic acid with a monovinyl compound while concomitantly thealpha-beta unsaturated acid is reacted with a monoepoxide to form ahydroxyester. More specifically, a styrene-hydroxy propyl acrylate orvinyl toluene-hydroxy propyl methacrylate copolymer is prepared bycombining acrylic acid or methacrylic acid, propylene oxide, and styreneor vinyl toluene, and the esterified copolymer-containing carboxylgroups is readily formed in the presence of an amine, an amine salt, ora salt of a quaternary ammonium hydroxide, etc., as a catalyst for thecarboxy-epoxy reaction and a peroxide or bydroperoxide, etc., as acatalyst for the copolymerization reaction. Again, sufficient acid isemployed so that the acid value of the resulting copolymer is betweenabout 1 to 50.

In preparing the carboxy-hydroxy copolymers following the practice ofSerial No. 593,340, now U.S. Patent No. 3,002,959 the three reactantsand the two catalysts are combined in the presence of a solvent which isinert insofar as the reactions are concerned, and refluxed until thecarboxy-epoxy esterification and concomitant [polymeriza'tion reactionsare substantially complete, as indicated by a relatively constant acidvalue, and a solidscontent approaching the theoretical for completeconversion. The reflux period generally is from four to ten hours. Theacid value continues to decrease until the reaction is substantiallycomplete, whereupon the acid value remains substantially constant. Therefluxtemperature is dependent upon the boiling point of the lowestboiling su-bstituent, and the amount of the substituent present in themixture. Thus, when propylene oxide, along with a higher boilingsolvent, is used, the reflux temperature is generally C. to C. Ingeneral, the reaction temperature is between 60 C. and the refluxtemperature of the mixture. It is noted that this invention involves theuse of two catalysts, where one catalyst is an inhibitor of the reactionpromoted by the other. Amines, for example, are inhibitors of vinylcopolymerization reactions. Accordingly, for maximum production of estergroups, as well as ultimate conversion to copolymer, it is desirablethat the two catalysts be in balance. If too much amine or similarcatalyst is used, the acid value will reach a leveling-off point, i

but the conversion to copolymer will be low. If too much peroxide .orother polymerization catalyst is employed, conversion to polymer issatisfactory but the leveling il of the acid value, indicating extent ofesterification of carboxyl groups, will not be reached to the properdegree. In general, the amount of peroxide is one to four per cent,depending upon the monomers, and thecarboxyepoxy catalyst is in therange of 0.5 to 6 percent by weight based on the reactants, dependingupon its basicity. Weakly basic catalysts such as tertiary amines areused in quantities of from three or four to six pe cent, while less ofthe stronger bases such as primary amine is used within the range.

Thus, as claimed in Serial No. 593,340, now U.S. Patent No. 3,002,959, aone-step process was provided for preparing carboxy-hydroxy copolymerswherein the aliphatic acid and the monoepoxide are reacted using amineor a quaternary ammonium compound as a catalyst, while the unsaturatedaliphatic acid is concomitantly copolymerized with the ethylenicallyunsaturated monomer. In the preparation of these carboxy-hydroxycopolymers-for maximum yields, it is also desirable to maintain a properproportion of reactants to solvent. When too much solvent is used, thecarboxy-epoxy reaction proceeds normally but there is a low conversionto polymer. If too little" solvent is employed, production of estergroups from the carboxyl-epoxide reaction is low whereas thepolymerizatlon reaction proceeds without difficulty. For most purposes,it is desirable to employ the solvent in a ratio of the com bined threereactants to solvent of from 110.4 to 1:1.

Among the monoepoxides suitable for the preparation of ester groups inaccordance with this invention are substituted alkyl compounds, as Wellas ethers and esters. One class of carboxy-hydroxy copolymers resultsfrom the reaction of the carboxyl groups of the alpha-beta unsaturatedacid, with a saturated hydrocarbon, ether, ester, etc., having athree-membered epoxide ring, said epoxy compound being free of otherreactive groups. Examples are oxirane, or ethylene oxide, as well assaturated alkyloxiranes, for instance, methyl oxirane, or propyleneoxide, butene-Z-oxide, etc. Among others are esters and etherscontaining only one three-membered epoxide substituent, each free ofother reactive groups. Examples are phenyl glycidyl ether, isopropylglycidyl ether, butyl glycidyl ether, glycidyl benzoate, glycidylacetate, etc.

Valuable alpha-beta unsaturated acids for use in the preparation of thecopolymer are short chain alpha-beta unsaturated aliphaticmonocarboxylic acids such as acrylic acid, methacrylic acid and crotonicacid. By short chain alpha-beta unsaturated acids are intended those ofnot more than twelve carbon atoms. Included are half-esters of maleicand fumaric acids formed with saturated alcohols of from one to tencarbon atoms.

Copolymerized with the alpha-beta unsautrated acid, or the hydroxy esterof the alpha-beta unsaturated acid, is a monomer copolymerizabletherewith, containing a single active CH =C group, including a terminalmethylene group, which undergoes addition polymerization to producelinear polymers, in other words, a vinyl compound. Particularlyimportant are vinyl aromatic compounds, for instance, styrene, vinyltoluene, alpha-methyl styrene, the halostyrenes, etc., having a singlevinyl group and free of other substituents capable of reacting with anunsaturated acid, i.e., a monofunctional vinyl aromatic compound. Alsovaluable are saturated alcohol estersof acrylic, methacrylic andcrotonic acids. Examples of monofunctional vinyl aromatic monomers areisopropenyl toluene, the various dialkyl styrenes, ortho-, metaandpara-chloro styrene, bromo styrenes, fiuoro styrenes, cyano styrenes,vinyl naphthalene, the various alpha-substituted styrenes, e.g.,alpha-methyl styrenes, alpha-methyl para-methyl styrenes, as well asvarious di-, triand tetra-chloro, bromo and fluoro styrenes. Acrylic,methacrylic and crotonic esters of saturated alcohols include themethyl, .ethyl, propyl, isopropyl, n-butyl, iso-butyl, (sec)butyl,(tert)butyl, amyl, hexyl, heptyl, octyl, decyl, dodecyl, etc..esters ofacrylic, methacrylic, and crotonic acids. Thus, preferred vinyl monomersinclude alpha-beta unsaturated monocarboxylic acid esters of saturatedmonohydric alcohols, the acids having not more than four carbon atomsand the alcohols having not more than twenty carbon atoms andmonofunctional vinyl aromatic compounds.

Other known vinyl monomers can, of course, be used in the preparation ofthe carboxyl-containing vinyl copolymer. Desirable monomers includevinyl aliphatic cyanides of not more than four carbon atoms, forexample, acrylonitrile and methacrylonitrile, as well as monovinylethers, e.g., ethyl vinyl ether, ethyl me-thallyl ether, vinyl butylether, methyl vinyl ether and others of not over twenty carbon atoms.Included also are unsaturated monohydric alcohol esters of saturatedmonobasic acids wherein the alcohols contain a single vinyl group andthe acids have not morethan twenty carbon atoms, for instance, vinylacetate, vinyl stearate, and-the allyl, methallyl, and crotyl esters ofpropionic, butyric and other acids. Not only the vinyl monomersthemselves, but mixtures of'the vinyl monomers can be copolymerized withthe alpha:

beta unsaturated acids to form the carboxyl-containing vinyl copolymer.A particularly desirable mixture is a combination of an acrylic ormethacrylic ester with styrene or vinyl toluene.

In the preparation of ester groups, any of the catalysts which areactivators for epoxide-carboxyl reactions can be used. Theseepoxy-carboxy catalysts are generally basic materials and are well knownin the art, for example, amines, amine salts, quaternary ammoniumhydroxides and quaternary ammonium salts, such as dimethylaminomethylphenol, benzyl trimethyl ammonium hydroxide, benzyl trimethyl ammoniumchloride etc. Particularly useful for this purpose are the quaternaryammonium hydroxides and halides.

Included among catalysts for promoting the polymerization of thealpha-beta unsaturated monocarboxylic acid with the vinyl monomer arehydrogen peroxide, various organic peroxides, for example, ascaridol,acetyl,

' and benzoyl peroxide, dibutyryl and dilauryl peroxides,

caprylyl peroxide, as well as partially oxidized aldehydes which cancontain peroxide, ureaperoxide, succinic acid peroxide, and the like.Other peroxides are fatty acid peroxides, such as coconut oil peroxides,stearic peroxide, lauric peroxide, and oleic peroxide. Also intended arealcoholic peroxides such as tertiary butyl hydroperoxides and otherperoxides such as cumene hydroperoxide, tertiary butyl perbenzoate,hydroxyheptyl peroxide and chlorobenzoyl peroxide. Other free radical.promoting catalysts suchas azobisisobutyron-itrile can also he used.

By combining the three reactants according to Serial No. 593,340, nowPatent No. 3,002,959, and application Serial No. "117,830, filed June19, 1961, a wide variety of carboxy-hydroxy copolymerscan be prepareddepending entirely upon the ratio of vinyl monomer to the other tworeactants. C arboxy-hydroxy copolymers particularly useful in thecoatings field are generally prepared so that the carboxy-hydroxycopolymer contains from five to seventy-five percent by weight, based.on the copolymer of the hydroxy ester of the alpha-beta unsaturatedmonocarboxylic acid. Hence, the remaining ninety-five to twenty-fivepercent of the copolymer is vinyl compound. The maximum amount ofmonoepoxide will, generally, of course, be that equivalent to less thanthe unsaturated monocarboxylic acid, such that the acid value of theresulting copolymer will be about 1 to 50. In general, copolymers havean average of-from four to one hundred hydroxyl groups per molecule, andweights per hydroxyl group of not less than 116. It has been noted thatin the incorporation of the carboxy-hydroxy copolymers, asolventisemployed as the reaction medium. Desirable solv'ents for.this-purpose are ketones, Cellosolves and aromatic hydrocarbons as wellas combinations of aromatic hydrocarbons. With a ketone or Cellosolve,for example, acetone,,methyl ethyl ketone, methyl iso-butyl ketone,diisobutyl ketone, Cellosolve, Cellosolve acetate, and mixtures ofketones andCellosolves with xylene, toluene, benzene, etc.

As pointed out above, the canboxy-hydroxy copolymers of this inventionare useful in the coatings industry and are eminently suitable ascrosslinking agents Withdiisocyanates,- epoxides, and aminoplast resins.

The presence of the carboxyl groups in the copolymer prepared accordingto the present invention are of particular importance in that thesecarboxyl groups impart to the copolymer a unique compatibility with thecrosslinkingagent, such as.an alkylated aminoplast resin, andconsequently these, copolymers produce a crosslinked product havingavery high gloss. On the other hand, thelabsence of the carboxyl groupsresults, in the production of crosslinked products having substantiallyless gloss.

' The presence of the carboxyl groups in the copolymer of this inventionis also of particular significance in imparting stability to thecopolymer when the copolymer is' present in an uncured-mixturecontaining the crosslinking agent, such as a diisocyanate. Thisstability feature is important because these copolymers are generallysold in admixture with the crosslinking agent. It is therefore ofparamount importance that no substantial crosslinking reaction takeplace between the copolymer and the crosslinking agent during theshipping and storage periods.

The consumer who purchases the admixture and who coats various articleswith it, usually follows a procedure whereby he fills a dip tank withthe admixture and then dips the articles in the tank. He then removesthe coated articles from the tank andthen bakes them. During the bakingperiod, a self-crosslinking reaction takes place between the copolymerand the crosslinking agent. Since it is customary to simply replenishthe contents of the dip tank as they become depleted, it is apparentthat portions of any particular admixture batch may remain in the diptank for extended periods of time. It is again of paramount importancethat no substantial crosslinking reaction take place between thecopolymers and the crosslinking agent during the period of time in whichthe admixture is in the dip tank.

It has been found that when a crosslinking agent, such as an alkylatedaminoplast resin, is employed, and the acid value of the copolymersproduced according to the present invention approaches zero, an acidcatalyst must be added to the copolymer-crosslinking agent mixture inorder to produce a self-crosslinking mixture. This mixture, however, isnot satisfactorily stable. The copolymers of this invention require noadditional acid catalyst and yet they are surprisingly stable whenpresent in an uncured mixture containing the crosslinking agent. If thestability of the mixture is not of primary concern, small amounts ofacid catalysts may be added to the mixture in some instances.

For a further understanding of the invention, reference is made to thefollowing specific examples, the viscosities given being Gardner-Holdtviscosities run at 25 C. These examples are intended to be illustrativeof the invention only, since ditferent embodiments can be made withoutdeparting from this invention.

I Example 1 -A carboxy-hydroxy containing copolymer is prepared bycharging into a two liter flask equipped with agitator, thermometer andreflux condenser, 53 5.0 grams of methyl isobutyl ketone. To thissolvent is added 178.5 grams of propylene oxide, 221.6 grams of acrylicacid and 400.0 grams of styrene. The ratio of the three reactants tosolvent used is 1.0 to 0.67. In addition to the 178.5 grams of propyleneoxide, a percent (17.9 gram) excess is used to compensate for any lossdue to volatility; the unreacted portion being distilled off at thecompletion of the process. To this mixture, ascatalysts, are added 16.0grams of benzoyl peroxide, and 22.9 grams .of a 35 percent solution ofbenzyl trimethyl ammonium hydroxide in methanol. The contents .of theflask :are heated to reflux temperature (,7580 C.) at which time anexothermic reactionoccurs and heating is discontinued. After theexotherm subsides, heat again is .applied to maintain refluxing untilanacid value of 2.7 isgreached (approximately ten hours). The flaskcontents are further heated to about 117 C. while distilling off anyunreacted propylene oxide. After removal of the excess propylene ox ide,the reaction mixture is cooled to about 70 C. and poured into a suitablecontainer. This .process results in a 50-50 copolymer of styrene and.hydroxy .propyl acrylate by combination of these proportions; 22.3parts by weight of propylene oxide, "27.7 parts by weight vof acrylicacid and ;50.0 parts by weight of styrene, a total of 1-00 parts for thethree reactants. The copolymer solution thus preparedzhasa viscosity ofZ (Gardner-Helm) and @1585 .percentsolidscontent.(two hours at 150 C.).

6 Example 2 A carboxy-hydroxy-containing copolymer is prepared according.to Example 1 by combining 44.4 grains (11.1 parts by weight) ofpropylene oxide, 55.6 grams (13.9 parts by weight) of acrylic acid, and300.0 grams (75.0 parts by weight) of styrene (parts by weight based ona totalof 100 for the three reactants). 266.5 grams of xylene are usedas a solvent. The ratio of the three reactants to solvent used is 1 to0.67. As catalysts are added 4.0 grams of benzoyl peroxide and 5.7 gramsof a 35 percent solution of benzyl trimethyl ammonium hydroxide inmethanol. Refluxing of the mixture is continued until an acid value of1.5 is reached (approximately 12 /2 hours). The 7 52 5 styrene-hydroxypropyl acrylate copolymer solution prepared has a solids content of 51.3percent (two hours at" 150 C.).

Example 3 A carboxy-hydroxy-containing copolymer is prepared accordingto Example 1 by combining 66.9 grams (22.3 parts by weight) of propyleneoxide, 83.1 grams (27.7 parts by weight) of acrylic acid, 75.0 grams (25parts by weight) of styrene and 75.0 grams (25 parts by weight) ofmethyl acrylate (parts by weight being based on a total of 100 parts forthe four reactants), in the presenceof 300.0 grams of xylene. The ratioof the four reactants to solvent used is one to one. To this mixture areadded as catalysts three grams of benzoyl peroxide and 8.6 grams of a 35percent solution of benzyl trimethyl ammonium hydroxide in methanol. Inaddition to the 66.9 grams of propylene oxide, a ten percent excess (6.7grams) additional are used to compensate for any loss due to volatility;the unreacted' portion being distilled ofi at the completion of theprocess. The reaction mixture is heated to reflux temperature at whichtime an exothermic reaction takes place andheating is discontinued.After the exotherm subsides, heat is again applied and refluxingislcontinued until an acid value of 3.7 is reached (approximatelyelevenhours). Unreacted propyleneoxide is distilled off, the contents of theflask are cooled .to around C. and ,are then poured'into a suitablecontainer. This styrene-methyl acrylate-hydroxy propyl acrylatecopolymer solution (25-25-50), prepared from the proportions above, hasa solids content of 43.1 percent (two hoursat 150 C.).

car-boxy-hydroxy-containing copolymer is prepared from 66.9 grams (22.3parts by weight) of propylene oxide,

83.1 grams (27.7 parts byweight) of acrylic acid and 150.0 grams (50.0parts by weight) of vinyltoluene (parts by weight being based on a totalof parts for the three reactants). As solvent 200.0 grams of xylene areadded. The ratio of the three reactants to solvent used is one to 0.67.To this mixture are added as catalysts, 6.0 grams of benzoyl peroxideand 8.6 grams of a 35 percent solution .of benzyl trimethyl ammoniumhydroxide in meth-. anol. In addition to the 66.9 grams of propyleneoxide, 6.7 grams (ten percent excess) are added to allow for any lossdue to volatility; the unreactedportion being distilled ofl at thecompletion of the process. The reaction mixture isrefluxed until an acidvalue of 1.2 is obtained (approximately 10 /2 hours). The 5050 vinyltoluenehydroxypropyl acrylate copolymer solution thus prepared las asolids content of 46.2 percent (two hours at ampl A .carboxyehydroxy'containing copolymer is prepared according to Example .4 :by combiningin the presence of 100.0 grams of xylene and 100.0 grams of ethylCellosolve, 65.3 grams (22.3 parts by weight) of propylene oxide, 81.0grams (27.7 parts .by weight) of acrylic acid and 146.4 grams (50.0parts by weight) of vinyl toluene (parts by weight being based on thetotal of 100 parts for the three reactants). The ratio of reactants tosolvent used is one to 0.67. Benzoyl peroxide in the amount of 6.0 gramsand triethanolamine in the amount of 18.0 grams are added as catalysts.The 50-50 vinyl toluenehydroxypropyl acrylate copolymer solutionresulting from the proportions above has an acid value of 3.7(approximately ten hours refluxing), and a solids content of 43.9percent (two hours at 150 C.).

Example 6 A carboxy-hydroxy containing copolymer is prepared accordingto Example 1, by combining in the presence of 267.0 grams of methylisobutyl ketone, 80.4 grams (20.1 parts by Weight) of propylene oxide,119.6 grams (29.9 parts by weight) of methacrylic acid, and 200.0 grams(50.0 parts by weight) of vinyl toluene (parts by weight being based ona total of 100 parts for the three reactants). The ratio of the threereactants to solvent used is one to 0.67. To this mixture are added ascatalysts, 8.0 grams of benzoyl peroxide and 6.7 grams of a 60 percentaqueous solution of benzyltrimethyl ammonium chloride. Combination ofthe proportions above result in a 50-50 vinyl toluene-*hydroxypropylmeth-acrylate copolymer solution with an acid value of 9.6 (afterapproximately 8 /2 hours refluxing) and a solids content of 56.7per-cent (two hours at 150 C.).

Example 7 According to the process outlined in Example 1, acarboxy-hydroxy containing copolymer is prepared in the presence of200.0 grams of methyl isobutylketone by combining 112.2 grams (37.4parts by weight) of butyl hydrogen maleate, 37.8 grams (12.6 parts byweight) of propylene oxide, and 150.0 grams (50.0 parts by weight) ofmethyl acrylate (parts by weight being based on the total of 100 partsfor the three reactants). The ratio of the three reactants to solventused is one to 0.67. Six grams of benzoyl peroxide and 2.5 grams of a 60percent aqueous solution of benzyl trimethyl ammonium chloride are usedas catalysts. The copolymer resulting from the combination of theproportions above is a 50-50 methyl acrylate-hydroxypropyl butylmale'ate copolymer solution with an acid value of 12.9 (refluxing forapproximately ten hours) and a solids content of 40.7 percent (two hoursat 150 C.).

Example 8 According to the procedure outlined in Example 1, acarboxy-hydroxy containing copolymer is prepared by combining in thepresence of 200.0 grams of methyl isobutyl ketone, 101.4 grams (33.8parts by weight) of phenyl glycidyl ether (weight per epoxide=150), 48.6grams (16.2 parts by weight) of'acrylic acid, and 150.0 grams (50.0par-ts by weigh-t) of styrene (parts by weight being based on a total of100 parts for the three reactants). The ratio of the three reactants tosolvent used is one to 0.67 As catalysts, 6.0 grams of benzoyl peroxideand 5.0 grams of a 60 percent aqueous solution of benzyl trimethylammonium chloride are added. The mixture is refluxed until an acid valueof 3.4 is reached (approximately eight hours). The above proportionsresult in a 5050 styrene-acrylic acid ester of phenyl glycidyl ethercopolymer solution, with a solids content of 55 percent (two hours at150 C.).

Example 9 A carboxy-hydroxy containing copolymer is prepared bycombining in a one liter flask fitted with a thermometer, condenser andagitator, in the presence of 200 grams of methyl isobutyl ketone; 97.5grams (32.5 parts by weight) of butyl glycidyl ether (weight per epoxide:133), 52.5 grams (17.5 parts by weight) of acrylic acid and 150.0 grams(50.0 parts by weight) of vinyl toluene (parts by weight being based ona total of 100 parts for the three reactants). The ratio of the threereactants to solvents used is one to 0.67. As catalysts are added sixgrams of benzoyl peroxide and five grams of a 60 percent aqueoussolution of benzyl trimethyl ammonium chloride. The mixture is heated toreflux temperature, at which time an exothermic reaction occurs andheating is discontinued. After the exotherm subsides, heat is againsupplied and refluxing is maintained until an acid value of 3.8 isreached (approximately 5 /2 hours). The 5050 vinyl toluene-acrylic acidester of butyl glycidyl ether copolymer solution prepared from theproportions above has a solids content of 60 percent (two hours at 150C.).

In accordance with this invention, it has been found that thecombination of an aminoplast resin with a carboxyl containing hydroxylcopolymer, such as the copolymer-urea aldehyde composition disclosed inSerial Number 593,340, now US. Patent No. 3,002,959, and applicationSerial Number 117,830, filed June 19, 1961, yields composition-s havingoutstanding properties. Such copolymer-aminoplast resin compositionslend themselves very readily to the formation of industrial finishes.They are excellent coatings for metal surfaces, such as for stoves,refrigerators, washers, driers, and other appliances as well asautomobiles, toys, and the like.

Aminoplast resins, as contemplated herein, include alkylated condensatesformed by the reaction of aminotriazines and amino-diazines with:aldehydes. It is known that various amines and amides Will condense inthe presence of alcohols with aldehy-des to form alkylatedaldehyde-amine and aldehyde-amide condensates. Thus, urea, thiourea, andvarious substituted ureas and urea derivatives will react with aldehydessuch as formaldehyde to form alkylated condensates, e.g., 'methylolure-as, etc. Similarly, it is well known that melamines, such asmelamine itself and benzoguanamine will react with aldehydes,particularly formaldehyde, to form melaminealdehyde condensates. Variousother amines and amides can similarly be reacted with formaldehyde,etc., to form alkylated condensates which are alkylated amine aldehydeor amide aldehyde resins or condensates. Alky-lated condensates resultwhen the amino aldehyde or amide aldehyde resin is prepared in thepresence of alcohols such as methyl, ethyl, propyl, butyl, isobutyl,octyl and decyl alcohol, 'these solvents actually becoming a part of theresulting product. In general, alkylated urea or melamine aldehydecondensates of different degrees of condensation can be used so long asthey are soluble in aromatic hydrocarbons or mixtures of these withother solvents. Alkylated melamine-aldehyde condensates, however, arethe preferred aminoplast resins.

The proportions of the carboxy-containing hydroxyl copolymer and theaminoplast resin will depend on the desired properties of the coatingwhich results on curing at a temperature of C. to 150 C. It is usuallypreferred that the composition contain 5 to 50 percent aminoplast resinand about .2 to 4 percent acid, the remainder being a comonomercopolymerizable therewith. Based on the foregoing, this invention thuscontemplates a heat hardenable coating composition especially forapplication to metal, based on a mixture of (1) 50 to percent of athermoplastic copolymer of (a) 0.2 to 4 percent acrylic acid,rnethacrylic acid, crotonic acid or half acid esters of maleic andfumaric acids, (b) 1 to 71 percent of a hydroxy ester of an acid ofgroup (a) and a monoepoxide such as 1,2-alkylene oxides, aryl1,2-alkylene oxides, monoglycidyl ethers and monoglycidyl esters, eachhaving not over 10 carbon atoms and (c) 25 to 95 percent, the totalbeing of an ethylenically unsaturated monomer copolymerized therewith;with (2) 5 to 50 percent of an aminoplast resin. In a specificembodiment, the invention includes a heat hardenable coating composition9 based on the mixture of plastic copolymer of (a) to 30 percenthydroxypropyl acrylate, methacrylate or crotonate, (b) 1 to 4 percentcrotonic, acrylic or methacrylic acid and (c) 66 to "94 percent, thetotal being 1000f at least one other co- 1) 50 to 95 percentthermo- 7 10xylol solution. At curing schedules of 200 C. for minutes and 200 C. for30 minutes, hard, mar resistant, thermoset films are produced.

Four additional blends and films are prepared in the same manner asabove. The reactants and quantities used 5 polymerlzablemonoethylemcally unsaturated monomer and the proportions of the curedfilms are listed in the and (2) 5 to 50 percent of the aminoplast resin.following table:

Copoly'mer Urea-Form- Blend Solution aldehyde Curing Properties CuringTime, 15 min.

(parts) Resin Sclu- Temp., 0.

tion (parts) 10b; 4 200 Tough,-flexible,fair mar resistance. 10c 20 6. 8200 Very tough and more flexible than Blend 10b, good mar re- 1 sistanceand adhesion. 10d 20 10. 7 200 Extremely tough and hard, very goodadhesion, excellent mar resistance. 10c 20 16.0 200 Fairly brittle,extremely hard,

good adhesion, excellent mar resistance.

" These coatings are exemplified further by the follow- Example 1] ingpreparations: I

Example 10 Material Units Parts by Weight I 7 Pro lene Oxid l0 ercentcess b Mat ial. mts P gggg m H p ex y 10.9 33.0

tasti st??? '13:: i332 3313 ggq Peroxide 3 3 Styrene; 77. 232.8 g ft 1 tBnzoylPernxiria V v 6.0 v Y 11 Y Ke 12m) enzyl TrimethylArnmoruumAcetate 3.0 Methyl Isobutyl Ketone 180. 0 1

Inaccordance with Example 1, the 30 parts of propyl-I ene oxide, 37.2parts of acrylic acid, 232.8 parts of sty- As in the procedure ofExample 10, the above materene, 6 parts of benzoyl peroxide, 120 partsof Xylene and 40 rials in the amounts shown are .heated to reflux (80?C. to the 180 parts of methyl isobutyl ketone are heated ,With 90 C.),at which temperature an exothermic reaction agitation to reflux (80 Q...to 90 C.). At this temperaoccurs. After the exotherrn subsides thereaction mixture ture an exothermic reaction occurs and heating isdisconis again heated to maintain refluxing (raising the temperatinned;After the exotherm-subsides heat is again applied ture to 122. C. asreflux permits) until an acid value to-maintain refluxing (raising thetemperature to 117 C. (solution) of 2.6 is reached (about 9 hours). Theresultas reflux permits); After 10 hours of refluxingp-the acid ingcopolymer solution at a solids content of 44.8 percent valueof thesolution is 40.5. Accordingly, .3 gram of has an acid value of 5.8(solids basis). Blends are made benzyl trimethyl ammonium acetate isadded followed of the above 44.8 percent solids copolymer solution withone and one-half hours later by another addition of .6 the percentsolids urea-formaldehyde resin solution gram of benzyltrimethyl ammoniumacetate. The-solu- 50 described in Example 10 in the same way as theblends tion is further heated until its acid value is 10.7. The finalgreater, a styrene-hydroxy propyl acrylate-acrylic acid copolymersolution having a solids content of 47.9 percent, has an acid value of22.3 (solids basis).

of Example 10. Films are also prepared from the blends. The followingtable lists the quantities of the reactants used, the curing schedule ofthe films, and a comparison of the properties of the cured films.

- copolymer Urea-Formal- Curing Curing Blend Solution dehyde ResinTemp., C. Time Properties e (parts) "solution (parts) 11a M 30 4 200 15Brittle.

11b 30 5.6 200 15 Less brittle than 11a, fair mar resist Y 8.1108.

110 30 9. 6 200 15 Very hard, good adhesion and good mar resistance. 11d30 15 200 15 Tough, hard very good mar resistance most flexible oi thefour.

Minutes =Inasuitable container, 20 parts of the above copolymer Sixadditional blends and films are prepared inthe solution (47.9 percentsolids) and 1.8 parts of a ureaformaldehyde resin solution are blendedand 3 mil films of this blend. (Blend 1011) are drawn down on glassplates. The-urea-formaldehyde resin solution used is at 60/30/10butylated urea-formaldehyde resin/butanol/ same way as above. However,these blends have a morpholine salt of para-toluene sulfonic acid addedto them as a catalyst. The following table lists the quantities of thereactants used, the curing schedule of the films, and a comparison ofthe properties of the cured films.

Urea- Catalyst Copolymer Formaldehyde (25 Percent Curing Curing BlendSolution Resin Solution in Temp, C. Times 3 Properties (parts) SolutionEthanol) (parts) 2 (parts) lle 30 .9 150 30 M%r1re1sistance better thanBlend 11d, r tt 6,. 11f X 30 9.6 .8 150 30 Good hardness, flexibilityand'mar resistance. 11f 200 Less mar resistance and less flexibilitythan Blend 11f. 11g 1 30 5. 6 7 150 30 Good mar resistance, moreflexible than Blend 11f. 11g- 200 20 Less mar resistant flexibility thanble 1d 1li. 11h 30 9. 6 1. 6 150 30 Good mar resistance, less flexiblethan Blend 11g. 11i 3O 5. 6 1. 4 150 30 Poor to fair mar resistance.llj; 30 9. 6 27 4 150 30 Very much like blend 110.

1 44.8 percent solution. 2 60 percent solution. 3 Minutes. 4 BenzylTrimethyl Ammonium Acetate.

Example 12 raised to' reflux and refluxing is continued until a 98percent conversion to copolymer is obtained. The resulting MaterialUnits Parts by weight 20 copolymer solution (copolymer 1), at 45 percentresin Pm lene OX1 de 74 3 solids has a viscosity of J and an acid valueof 13.8 (solids i.A basis). The viscosity of the copolymer solution,when re- St em 0 duced to 40 percent resin solids with xylene is G.Benzoyl Perox1de 6.0 1 Xyle 120,0 To make a pastel blue, metallicautomobile ename us- Methyl Isobutyl Ketone 180.0 u f i cut asteBemmnmmy, Ammonium Meme 3.0 s the fvresomg copolymer, one p 0 a P a PFollowing Example 10, the above materials in the amounts shown areheated to reflux (80 C. to 90 C.), at which temperature an exothermicreaction occurs. After the exotherm subsides, heat is applied to theflask contents to maintain refluxing (raising the temperature to 126 C.as reflux permits) until an acid value (solution) of 14.7 is reached(about 13 hours). At the end of this time, 25.8 additional parts ofpropylene oxide are added to the flask contents and the reaction mixtureis heated to 126 C. over a period of six and one-half hours, distillingoff any excess propylene oxide at the end of this period. The resultingstyrene/hydroxypropylacrylate/acrylic acid copolymer solution having asolids content of 47.8 percent, has an acid value on solids basis of30.7.

Blends are made of the above copolymer solution with theurea-formaldehyde resin solution described in Example 10 and amorpholine salt of para-toluene sulfonic acid as a catalyst inaccordance with the catalyzed blends of Example 11. In addition, 10parts of methyl isobutyl ketone are incorporated in three of the blends.The following table lists the quantities of the reactants used, thecuring schedule and a comparison of the properties of the cured films. 1

previously prepared by mixing the solution of the copolymer andphthalocyanine blue in a sand grind mill ina ratio of four partscopolymer (based on solids). to one part phthalocyanine blue, is stirredwith an additional 62.25 parts,.based on solids, of the copolymer,employed. as a 45-percent solution. While this mixture is being stirred,16.75 parts of an isobutylated melamine-formaldehyde resin solution isadded containing percent resin in isobutyl alcohol. In addition, 6.46parts of a para: toluene sulphonamide-modified melamine-formaldehyderesin solution is added containing 66 percent resin in xylene. Stirringis continued and 6.93 parts acetone and 1.73 parts xylene are added.This mixture is then stirred until a smooth enamel forms. The enamel,when applied to an automobile body and baked at 250 F. has excellentfilm properties.

- Example 14 In a three neck, round bottom flask equipped with anagitator, thermometer, dropping funnel and reflux condenser, 1050 partsof xylene are heated to reflux. To this hot solvent the firstoftwomonomer additions is made consisting of 270 parts of methylmethacrylate, 45 parts of methacrylic acid, 180 parts of styrene and 75parts of cumene hydroperoxide. The temperature is heated to theCopolymer Urea- Methyl Solution (47. 8 Formaldehyde Catalyst IsobutylCuring Curing Blend Percent Resin Solution (parts by Ketone Temp., TuneProperties Solids) (parts (parts by weight) (parts by 0. (min) byweight) weight) weight) 30 6 .7 10 150 30 More flexible than Example 11cures,

good mar resistance. 30 10.3 .8 150 30 Brittle, but very good marresistance. 30 3.6 .7 10 150 -30 Good toughness, poor mar resistance. 302.7 .7 10 150' 30 Slightly inferior to blend 12c cure in I toughness andmat resistance.

* percent solution. r

Example 13 reflux temperature of 262 F., and at this temperature,

In a twelve liter, three neck, round bottom flask equipped with anagitator, thermometer, dropping funnel and reflux condenser, 3632.1parts xylene and 682.4 parts butanol are heated to reflux. To this hotsolvent over a period of 1 /2 hours, 1104.8 parts of methylmethacrylate, 1121.6 parts of butyl methacrylate, 426.7 parts of butylacrylate, 468.8 parts of ethyl acrylate, 375.0 parts of methacrylic acidand 37.5 parts of bcnzoyl peroxide are added. The mixture is heated atthe reflux temperature, 256 F., for two hours. The reaction product isthen cooled to 180 F. and 21.2 parts of a 40-percent solution of benzyltrimethyl ammonium methoxide in methanol are added. Over a period of 1/2 hours, 253 parts of propylene oxide are added to the flask contents.The temperature is again the second monomer addition is made consistingof 469 parts of methyl methacrylate, parts of methacrylic acid, 330parts of styrene and 30 parts of cumene hydroperoxide. The flaskcontents are permitted to reflux for one hour and 15 minutes and thencooled to F. At this temperature, 8.5 parts of benzyl trimethyl ammoniummethoxide (as a 40-percent solution), are added and then, over athirty-minute period, 101 parts of propylene oxide are also added. Thecomposition is again heated to the reflux temperature and held at thistemperature until a 98 percent conversion to copolymer is obtained. Theresulting composition is reduced to 50 percent resin solids withbutanol. This 50 percent resin solids composition has a viscosity of X-Yand an acid value of 14 (solids basis).

i 40 percent resin solids is I-J.

By the pigmentation procedure described in connection with Example 13, asolid white enamel is made from this copolymer solution. A sand grind ismade from 21.07 parts of titanium dioxide, 4.26 .parts of xylene and2.67 parts of the copolymer solution (based on solids). This grind isthen mixed with another pigment paste made from 42 parts (based onsolids) of the copolymer solution, 18.02 parts (based on solids) of amelamine formaldehyde resin made in normal butyl alcohol and having aviscosity of GK at 50 percent solids, 3 parts of Solvesso 100, anaromatic petroleum hydrocarbon, 4 parts of toluene, 2 parts of methylethyl ketone and .88 part of butyl Cellosol-ve. This mixture is stirreduntil a smooth enamel results, applied to an automobile body and bakedfor 30 minutes at 250 F. The resulting finish has very good properties.

The foregoing copolymer solution is blended on a solids basis withalkylated aminoplast resins in a ratio of 70 parts copolymer (solidsbasis) to 30 parts of each of the following resins:melamine-formaldehyde resin made in butyl alcohol and paratoluenesulfonamide (66 percent resin solids), benzoguanamine-formaldehyde resinmade in butyl alcohol (60 percent resin solids) butylatedmelamine-formaldehyde resin (55 percent resin solids), isobutylatedmelamine-formaldehyde resin (55 percent resin solids), butylatedurea-formaldehyde resin (50 percent resin solids). Films made from allof these blends, when compared with one fatty acid modified alkyd resincontaining 22.8 percent lauric acid and another one modified with 40percent soya acids, yield equivalent solvent resistance properties andsuperior resistance to lipstick and mustard staining.

Example 15 In accordance with Example 13, a copolymer solution isprepared in xylene using the followingz 46.90 parts of ethyl acrylate,37.35 parts of styrene, 9.40 partsof methacrylic acid and 6.35 parts ofpropylene oxide. The resulting copolymer solution (54.5 percent resinsolids) has a viscosity of Z Z and an. acid value of 12.6 (solidsbasis).

This copolymer solution is mixed with a paratoluene sulfonamide-modifiedbutylated melamine-formaldehyde resin in a ratio of 70 parts copolymersolids to 30 parts resin solids. The sulfonamide-modified butylatedmelamine-formaldehyde resin solution at 66 percentsolids in 34 percentxylene has a specific gravity of 1.06 and a viscosity of Z-Z The filmforming mixture of the copolymer solution with the melamine-formaldehyderesin solution is applied in the form of a film to steel panelspreviously coated with iron phosphate (Bonderite 1000). Films baked 30minutes at 250 F. have a pencil hardness of HB, pass the conical mandreltest but fail a -inchpound bump test. Films baked 30 minutes at 300 F.have a pencil hardness of F and pass both the conical mandrel and10-inch-pound bump tests.

Example 16 This copolymer solution is mixed in a 70 copolymer solids, 30resin solids ratio with a butylated melamine formaldehyde resinsolution, applied to Bonderite 1000 Solvesso 100: A95 percent aromaticpetroleum hydrocarbon having a bOlllIlg' range of 315 F. to 355 F. With90 percent boiling between 315 F. and 338 F,

steel panels and baked for 30 minutes at 300 F. The resulting slightlyhazy film has a pencil hardness of 2H and good mustard, catsup,lipstick, solvent, and boiling water resistance properties. When mixedin the same ratio with a butylated benzoguanamine-formaldehyde resinsolution, the baked film has good resistance properties and a pencilhardness of F. The butylated benzoguana-mine formaldehyde resin solutionat 60 percent solids in 20 percent butanol and 20 percent xylene has aspecific gravity of 1.04 and a viscosity of G-K.

Example 17 To a suitable reaction flask equipped with a mechanicalstirrer, thermometer, condenser and dropping funnel are added 50 partsof xylene and SO-parts of n-butanol. To the dropping funnel are added147 parts of styrene, parts of butyl acrylate, 45 parts of hydroxypropylmethacrylate, 18 parts of methacrylic acid and 6- parts of 'benzoylperoxide. Heat is applied to the flask raising the temperature of thesolvents to 90 C. Addition of the monomer-catalysts solution is begunand is continued for 3 hours and 5 minutes While the temperature of thereactants is allowed to rise to 120 C. Heating-is continued at 120 C.for 2 hours and 12 minutes. 3 partsof benzoyl peroxide are added to thereactants and heating is continued at 115 C. to 120 C. for 3 hours and14minutes. After the addition of 50 parts of xylene and 50 parts ofnbutanol, the resulting clear polymer solution has a viscosity of Z at62.2 percent solids.

To 22.5 parts of the polymer solution are added 1 parts of a butylatedmelamine-formaldehyde resin (at 60' percent solids in n-butanol andxylene) and 7.5 parts of xylene. Films are prepared on glass using a 3mil draw down blade. After a 30 minute bake at 150 C., well cured clearfilms are obtained with good mar resistance, adhesion and gloss.

Example 18 To a suitable reaction flask equipped with a mechanical.stirrer, thermometer, condenser and dropping funnel are added 50 .partsof xylene and 50 parts of n-fbutanol.

To the dropping funnel are added 156- parts'of vinyl ace tate, 90 partsof butyl acrylate, 9 parts of methacrylic acid, 45 parts ofhydroxypropyl methacrylate, and 6 parts of benzoyl peroxide catalyst.Heat is applied, raising the temperature in the flask to 90 C. Theaddition of the monomer-catalyst solution is begun andis continued overa 4-hour period While holding the temperature at C. to C. Heating iscontinued for twohours with the temperature slowly rising to 107 C.Additional catalyst, 3 parts benzoyl 'peroxide, and solvents, 50 partsxylene and 50 parts n-butanol, are added to the 'flask. Heating iscontinued at C. to 114 C. for 2.5 hours," The resulting clear producthas a Gardner-Holdt vi'scosity of'U toV at 58.1 percentsolidsJConversionofmonomers to polymers is 97 percent as calculated'from the solids determination.

-A blend is prepared from 24.1 parts of the copolymer solution, 10 partsof a butylated melamine-formaldehyde resin (at 60 percent solids inxylene and n-butanol) and 5.9 parts of xylene. Films are prepared onglass using a 3 mil draw down blade. After a 30 minute Fbake'at C.,well-cured films are obtained having excellent flexibility, adhesion,mar resistance and gloss.

Example 19 Using the same procedure as describedinExample 17,

a copolymer is prepared from 96 parts styrene, 150 partsethylacrylate,45 parts hydroxypropyl methacrylate and 9 parts methacrylic aciddissolved in 100 parts of xyleneand 100 parts of n-butanol using 9 partsof benzoyl peroxide catalyst. The copolymer solution has a viscosity ofZ at 61.4 percent solids. I

15 'To 22.9 parts of the copolymer solution are added 12 parts of anisobutylated melamine-formaldehyde resin (at 50 percent solids inisobutanol) and 5.1 parts of xylene. Films on glass are prepared fromthis blend using a 3 mil draw down blade. After a 30 minute bake at 150C., clear, hard, well-cured films are obtained having excellent marresistance and good adhesion, flexibility and gloss.

Example 20 To a suitable reaction flask equipped with a mechanicalstirrer, thermometer, condenser and dropping funnel are added 128 partsof xylene. To the dropping funnel are added 150 parts of ethyl acrylate,81 parts of styrene, 60 parts of butyl, hydroxypropyl maleate, 9 partsof methacrylic acid and 12 parts of di-tertiary butyl peroxide. Heat isapplied raising the temperature of the xylene in the flask to 130 C. Theaddition of the monomer-catalyst solution is begun and is continued for5 hours and 7 minutes while holding the temperature at 124 C. to 130 C.The temperature of the reactants is then held at 124 C. to 136 C. for 6hours, after which heating period, 100 percent conversion of monomers tocopolymers is obtained as indicated by solids determination. Theresult-, ing clear solution has a Gardner-Holdt viscosity of Z 22.9parts of the copolymer solution, 8.0 parts of an isobutylatedmelamine-formaldehyde resin (at 50 percent solids in isobutanol) and 9.9parts of xylene are blended together. Films are prepared on glass platesusing a 3 mil draw down blade. After baking for 30 minutes at 150 C.,the clear films exhibit very good mar resistance, gloss. toughness,adhesion and flexibility. These films are unaifected after 8 weeksimmersion in 5 percent NaOH solution.

Example 21 Using the same procedure as described in Example 17, acopolymer is prepared from 186 parts of vinyl acetate, 60 parts ofdibutyl fumarate, 45 parts of hydroxypropyl crotonate and 9 parts ofacrylic acid in 50 parts of xylene and 50 parts of n-butanol using 9parts of benzoyl peroxide catalyst. The copolymer solution has aviscosity of Z at 70.9 percent solids.

To 19.8 parts of the copolymersolution areblended 10 parts of abutylated urea-formaldehyde resin (dissolved at 60 percent solids in amixture of xylene and n-butanol) and 10.2 parts of xylene. Films areprepared on glass using a 3 mil draw down blade. After a 30-minute bakeat 150 C., films are clear and glossy.

Additional films are prepared in the same manner from a blend of 19.8parts ofthe copolymer solution, 10.2 parts of xylene and 10 parts of abutylated melamineformaldehyde resin (dissolved at 60 percent solids ina mixture of xylene and n-butanol). After a 30-minute bake at 150 C.,the films are clear and glossy.

Example 22 To 22.9 parts of the copolymer solution of Example are added8 parts of a polyisocyanate (adduct of 3 mols tolylene diisocyanate, 1mol trimethylol propane'and 3,,mols phenolisocyanate equivalentweight:335)' at 50% solids in ethylene glycol monoethyl ether acetate(80 parts copolymer to 20 parts diisocyanate compound on solids basis).After addition of 24.1 parts ethylene glycol monoethyl ether acetate, 3mil films are prepared on glass-Well cured films with very good adhesionto the glass are obtained after minutes at 180 C.

Another blend is prepared as described above wherein the ratio ofcopolymer to diisocyanate compound on a solids basis is 70 to 30. Films,prepared and baked as described above, are well cured and have very goodflexibility and gloss and adhesion to glass.

Example 23 A copolymer is prepared from 147 parts of vinyl acetate, 90-parts of butyl acrylate, 45 parts of hydroxypropyl crotonate and 18parts of methacrylic acid in 50 parts of xylene and 5 0 parts ofn-butanol using 9 parts of benzoyl peroxide catalyst. The copolymersolution at 68.1% solids has a Gardner-Holdt viscosity of Z to Z To 26parts of the copolymer solution are added 2.4

- parts of the diglycidyl ether of bisphenol A (epoxide equivalentweight:l), 11.6 parts of xylene and 0.2 part of a 60% aqueous solutionof benzyl trimethyl ammonium chloride. Films are prepared on glass usinga 3 mil draw down blade. After a 30-minute bake at C., well cured clearglossy films are obtained having excellent flexibility and adhesion toglass.

To 26 parts of the copolymer solution are added 2.4 parts of thediglycidyl ether of bisphenol A (epoxide equivalent weight=190), 0.2part of a 60% aqueous solution of benzyl trimethyl ammonium chloride and10 parts of an isobutylated melamine formaldehyde resin at 50% solids inisobutanol. After the addition of 11.6 parts of xylene, 3 mil films areprepared on glass and are baked at 150 C. for 30 minutes. Clear, Wellcured films hav ing very good mar resistance, excellent adhesion, andexcellent flexibility are obtained.

To 22.8 parts of the copolymer solution are added 9 parts of apolyisocyanate (adduct of 3 mols totylene diisocyanate, 1 moltrimethylol propane and 3 mols phenolisocyanate equivalent weight=335)at 50% solids in ethylene glycol monoethyl ether acetate. After theaddition of 8.2 parts of ethylene glycol monoethyl ether acetate, 3 milfilms are prepared on glass and are baked at C. for 30 minutes. Wellcured films having very good mar resistance and excellent flexibility,adhesion and toughness are obtained.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from'the spirit of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A copolymer of (a) 0.15 to 4.0 percent by weight of an unsaturatedaliphatic acid selected from at least one member of the group consistingof acrylic acid, methacrylic acid, crotonic acid and half acid-esters ofmaleic and fumaric acids formed with saturated alcohols of from 1 to 10carbon atoms, (b) 21 to 94.8 percent of at least one differentethylenically unsaturated monomer copolymerizable with the unsaturatedacid, and (c) 5 to 75 percent, the total being 100 percent, of a betahydroxy alkyl ester of an unsaturated aliphatic acid selected from atleast one member of the group consisting of acrylic acid, methacrylicacid, crotonic acid, and half acid-esters of maleic and fumaric acidsformed with saturated alcohols of from 1 to 10 carbon atoms, saidcopolymer having an acid value of from about l50.

2. The copolymer of claim 1 wherein (a) is acrylic acid, (b) is amixture of styrene and butyl acrylate, and (c) is hydroxy propylacrylate.

3. The copolymer of claim 1 wherein (a) is methacrylic acid, (b) is amixture of methyl methacrylate and ethyl acrylate, and (c) is hydroxypropyl methacrylate.

4. The copolymer of claim 1 wherein (a) is butyl hydrogen maleate, (b)is methyl acrylate, and (c) is hydroxy propyl butylmaleate.

5. The copolymer of claim 1 wherein (a) is acrylic acid, (b) is styrene,and (c) is 3-phenoxy, Z-hydroxy propyl acrylate.

6. The copolymer of claim 1 wherein (a) is acrylic acid, (b) is vinyltoluene, and (c) is 3-butoxy, 2-hydroxy propyl acrylate.

7. A composition comprising the copolymer of claim 1 in combination witha crosslinkin agent.

17 18 8. The composition of claim 7 wherein the crosslink- 3,028,3674/1962 OBrien 26077.5 mg agent 15 a dnsocyanate' 3,082,184 3/1963Falgiatore et a1. 260-851 References Cited 3,156,740 11/ 1964 Bussell260855 UNITED STATES PATENTS 5 MURRAY TILLMAN, Primary Examiner.2,681,897 6/1954 Frazler 260-86.1 3 002,959 10 19 1 Hicks 26() 83 1 J.C. BLEUTGE, Asszstant Exammer.

